The physiological significance of the Ca-transport of the erythrocyte membrane has been well documented. It has been established that the level of intracellular calcium controls cation permeabilities of the membrane as well as the cellular volume and shape. However, the details of these control mechanims are still unknown. Our preliminary results have demonstrated that the Ca-Mg-ATPase activity of the cytoskeleton of human red cell membrane (actin-spectrin complex) is enhanced by the addition of a regulatory protein complex isolated from the hemolysate. This regulatory protein complex contains at least three protein components, and resembles native tropomyosin of smooth muscle. Native tropomyosin prepared from smooth muscle was also found to activate the Ca-Mg-ATPase of the actin-spectrin complex. Two automated instruments have been built; an instrument to measure the relationship between oxygen tension and the viscosity of the suspension of sickle cells, and another instrument to measure the gellation time of sickle hemoglobin solution. Using these, it was shown that cetiedil, an anti-sickling drug, supresses the sickling not by the direct interaction with hemoglobin but by lowering the mean corpuscular hemoglobin concentration (by increasing the mean corpuscular volume). We propose to: (1) Isolate and purify protein components from the erythrocyte regulatory protein complex; (2) Determine physico-chemical properties of each protein component as well as its function in Ca-transport and in maintaining the size and shape of the cell; (3) Examine whether there is any abnormality in the function of the regulatory proteins of the sickle cell membrane; (4) Examine the effects of anti-sickling drugs on the Ca-Mg-ATPase activities of both the actin-spectrin complex and the ghost membrane; and (5) Examine the effects of anti-sickling drugs on the size and shape of erythrocytes.